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Socalmooneypilot

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    WJF
  • Model
    M20G

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  1. Like everyone else is saying here, it is hard to tell what condition the airplane is in. First off, does a G model suit your mission? I️ love my G, and it fits my desire of a low-cost 135-kt four-place bird perfectly. But the ‘C and ‘F models will do 10 knots better on the same fuel burn. It would be a bummer to get a G and then find that you outgrew it in a year. Secondly, you are taking a risk by purchasing an airplane that has been sitting. It might turn out fine, it might not. As Alex’s story shows, it can take a few hundred hours before corroded lobes start spalling. I️ bought my G after it had been flying ~10 hr per year for the last 8 years. I️ put 450 hours on it in 2 years and it’s running like a champ. Knowing what I️ know now, I️ probably wouldn’t have taken the risk. Sent from my iPhone using Tapatalk
  2. Thanks Bob for the link to Mike’s article. I️ did not know the story behind champion. I will do a resistance check at the next oil change, about 20 hours to go, unless something starts acting up sooner. Have most people switched to Tempest plugs at this point? I️ don’t mind replacing all 8 if there’s a compelling quality story to it.
  3. I love MooneySpace. In the end we found two smoking guns, and fixing both together solved the problem. Long writeup below for future searches. My A&P and I pulled off the cowling last weekend and found major problem #1. There was a fairly major leak at the intake flange for the right front cylinder. Blue 100LL dye was all over the intake, cylinder, and had even sprayed onto the inside of the cowling. Closer inspection found that one of the bolts securing the intake flange had backed out, and contributing to the problem was a cracked gasket. My A&P says a leak like this will cause the cylinder in question to run excessively lean, which likely explains the majority of the engine roughness. @kortopates gets credit for that one. What was interesting is that this was not the cylinder with the single EGT probe, and a subsequent test flight showed a smoother engine but still high temperatures. So we pulled the cowling again and focused on the cylinder with the probe, the left rear. As many of you suggested, we found significant lead deposits on the bottom plug. We elected to pull all eight plugs for a very thorough cleaning and gapping. The following test flight showed the temperatures were back to normal and the engine felt better than before. A few lessons learned- Next time I'll at least pull the cowling off before spooling up the experts at MooneySpace. It didn't take a rocket scientist to find the intake leak. My A&P suggests I clean/gap the plugs at each oil change, rather than at each annual. I'm in talks with my local avionics shop to install a used EDM-700. The quote I got for install was more reasonable than I expected and it is worth the piece of mind. It would have really helped in this situation.
  4. Thanks for the quick reply Carusoam. I'm using Champion plugs, standard type (not the fine wire ones). I lean religiously on the ground, and in flight at low power settings. I've never had any fouling issues, and my A&P always says the plugs look good at the annual. Last clean/gap was three months ago. Plugs have about 300 hours on them, all changed at the same time. I would love this to be a plug fouling issue, simple and cheap to fix. We did notice an ignition wire chaffing on the doghouse at last annual and wrapped it with electrical tape. I'm going to call the A&P and see if he has some time to check out the plugs and wiring next week, and get his thoughts on troubleshooting. Really wishing I had an engine monitor to help with this.
  5. Went for a test flight today, now I'm more confused. Takeoff was normal- nothing unusual about the EGT or engine vibration levels. I did a mag check in my climb configuration- WOT, 2600 rpm, 100 mias, full rich mixture. When I turn off one of the mags I get engine vibration and an EGT spike, identical to what I saw before. Behavior is the same on either mag. Going back to both mags makes things go back to nominal. Awesome, found the problem. It's been 8 years/400 hours since the last mag inspection, probably time for a mag overhaul. Then, back in the pattern, things get weird again. I'm at 17" MP and 2300 RPM, full rich mixture, and the EGT suddenly climbs again. This time it climbs right to my normal cruise temp, which I estimate is somewhere around 1450 deg. But here's the thing- I do another mag check, and I still get a drop on either mag. So both mags are functioning even when the issue is occurring, as far as I can tell. Additionally, I make the EGT go up and down with the mixture, but it still returns to the too-high temperature when I go back to full rich. I was able to make the EGT return to normal by throttling to idle, then back to 17". So in summary- Issue is intermittent, seems to come and go without warning, and happens at multiple power settings Mags and mixture control seem to be functioning normally, even when the issue is happening I wonder if this is a fuel distribution issue, or something going on with the cylinder that has the single EGT probe? I suppose the next step is to borescope the cylinders and look at the plugs? Other thoughts are appreciated!
  6. Definitely didn’t leave the carb heat on. That’s really interesting about the magneto failure causing those indications. I’m going to do an in-flight mag check to see if I️ can reproduce the symptoms when I️ get back in town this weekend. Unfortunately I only have the factory single-probe EGT without the temp markings, so I️ don’t know what the actual temps are. I️ just know it was high relative to my normal cruise point on the gauge. Frustrating to diagnose these things without a 4-Cylinder engine monitor. I’ve been trying to save that money for ADS-B, but maybe it’s time. Sent from my iPhone using Tapatalk
  7. Fuel pump was off, something I️ forgot on my checklist, bad on me. I️ did check the fuel pressure gauge when the issue happened, and it was indicating normally (about 4”). I️ have done a fuel system leak test by pressurizing the system with the electric pump, but not sure how to do it with the mechanical pump alone. Do you think this is a pump issue? Sent from my iPhone using Tapatalk
  8. Flight was at Bakersfield, BFL, and this was on climb out at a near standard day so density altitude was around 1,000’. Sent from my iPhone using Tapatalk
  9. Hi there, I’m a long time lurker on the forum hoping to tap the collective knowledge here regarding a strange issue I️ saw yesterday. Airplane is a ‘68 M20G with the carbureted O-360 engine Following a missed approach, I️ went to full throttle with mixture full rich. After a few seconds at full power, the engine began to vibrate and I️ noticed the EGT needle (factory single-probe) spike very high, past my normal cruise setpoint. I️ messed with the mixture knob for a second, and the vibration ceased and the EGT fell back down to normal. I️ can’t tell if messing with the knob actually fixed the problem, or if it was coincidence. Everything I️ experienced seemed consistent with suddenly having the mixture leaned passed peak, but I️ didn’t touch the mixture knob before the problem occurred. Any thoughts as to what on earth happened? Engine has about 9 years and 400 hours since major overhaul. It has flown over 100 hours/year for the last three years without missing a stroke. Thank you all!
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